What is Quantity Take-off?
Quantity take-off (quantity surveying) is a process that includes detailed calculations of supplies’ quantity and manpower required to finish a building project.
Quantities of each different building element to be used in the construction of the construction are calculated in the quantity. These calculations are turn into a table and the amounts of work also are calculated in detail.
Since each building element is a different measurement unit, the calculation of the building elements should be done separately and correctly. The accuracy of the quantity will ensure that the resulting cost is realistic.
Quantity Take-off Using BIM
Building elements are modeled in 3D in computer environment in accordance with building information modeling (BIM) standards. By assigning appropriate parametric properties to these 3D building elements, a more accurate and reliable quantity take-off is obtained.
Within the 3D parametric information there is information such as element quantities, dimensions of the elements and specific contract codes.
The Importance of BIM in Quantity Take-off
Quantity studies are important for the control of the project cost from the beginning of the project. The accuracy of the calculations is an important stage that should be an integral part of every large-scale project to prevent financial losses and project delays.
Quantity studies made on two-dimensional drawings can give untrue results due to a high error rate and miscalculations, since these are mostly not automated processes. In order to avoid such problems, data production with BIM supported quantity take-off and cost calculation is a superior method in terms of getting accurate and reliable results.
Measurement Units in Quantity Take-off
As you know, all units of measurement may differ from each other. For instance, length is measured in meters, area in square meters and volume in cubic meters. For this reason, units must be taken into account when calculating quantities. Because the cost calculation is created by multiplying the units of measure by the unit cost.
What Are the Units of Quantity Used?
Smooth Flooring, Borders, Timber lengths, Perimeters
In square meters:
Cladding, Brick Wall, Plastering, Paint Works, Shoring, Molds, Whitewash, Scaffolding, Mosaic, Insulation, Wood Joinery, Glass
In cubic meters:
Excavation works, Soil transport, Blockwork, Concrete work, Filling works, Room volume
Reinforced Concrete, Iron and other iron works, Aggregates, Load capacities
What Is a Quantity Table and Why Do You Need One?
The ‘bill of quantities’ is the document in which the details, categories and quantities of the materials and other expense items to be used in a construction project are written. A detailed analysis of the drawings and specifications for a correct understanding is very important in the preparation of the bill of quantities.
A bill of quantities is needed at every stage of the projects, but the need for a bill of quantities may differ depending on the agreement of some contracts and projects. The purpose of the meter scale is:
- To give the builders a clear idea about the works that need to be done in the project
- It gives the contract amount, which is important for employers and contractors
- The scope of the work to be done is defined
- It forms the basis for evaluating the changes
It is important to transfer the metering sheet to 3D-dimensional BIM building elements.
There are many programs that we can do building information modeling with such as Archicad, Revit, Allplan and Tekla, depending on what kind of project is being undertaken.
For each project, modeling begins with project naming in accordance with office standards. The project building structure is opened by considering the project coordinates, number of floors and height. A smart model is made by assigning attributes to architectural or static building elements. Attributes such as name, material, code, calculation mode, measure scale, unit of measure are assigned to the building elements.
- Name: It is modeled by providing unique, distinctive names for each building element. These names are important elements for the quantity surveying.
- Material: This is the parameter where the materials of the construction element are given.
For the quantity and cost based on two-dimensional projects, building information models (BIM) are carried out by giving appropriate quantifications to the building elements. For accurate metering results, the elements must be modeled at the right elevations, with the right quantities, not intersecting with any element and without any geometric errors. Accurate quantity data can be obtained by our report system which we have created using the right models and our vast experience in the sector.
How The Quantity Take-off Process Works?
Quantities of building elements such as concrete, columns, beams, slabs, walls, finishing works, doors and windows, excavations, excavations, roads, bridges, ventilation electrical and installation systems can be easily obtained from the building information models (BIM).
- Concrete, Column, Beam, Slab, Wall: Quantities of architectural or static structural elements in the project are taken according to their qualities such as floor information, thicknesses and materials.
- Finishing Works: The floor, ceiling and wall covering qualities assigned to the rooms and the quantity of the skirting boards are taken with appropriate reports.
- Doors & Windows: Information about the name, material, length, height, area of the building elements, in which rooms and on which wall the space is opened are taken from the models.
- Ventilation Pipes: They are modeled according to their dimensions, transport elements and position in the plumbing system.
- Excavation, Excavation, Road: After the terrain is modeled, it is made by overlapping the road and excavation project.
By being in constant cooperation with the project stakeholders in the quantity process, legendary visuals are prepared from the three-dimensional model, which conveys that the project is finalized correctly, and the quantity qualifications are taken correctly. Special tables are prepared for finishing works such as door-windows and installations.
Cost Calculation Process
Calculation of project cost from the beginning of projects is an important process in terms of realizing the project and avoiding cost losses. Starting from the feasibility stage of the projects, it is necessary to manage the project economy well and to distribute the cost of the works according to the customer’s budget.
The project cost calculation is made by taking advantage of the up-to-date price archive we have with our experience in the sector, together with the correct calculation of the quantity.
How Does the Budget Evaluation Process Work?
This is the process of calculating how the client’s budget, in the initial phase of projects, changes as the project progresses, as the geometry changes with attributes added or removed. It is an important phase in which the cost of the project is evaluated with the changing economic conditions of the country, such as inflation, and solutions are sought, and suggestions are presented in order to complete the project process without being affected.
About The Bimgen Method
Our company standards have been established in the quantity and cost calculations we have developed with our experience in large projects we have carried out in Europe and in our own country. 3D models of two-dimensional projects are made with the rules specific to our company, and the reports and the requested information are taken from the model.